Field of the Disclosure
The present disclosure generally relates to a surge immune stage system for wellbore tubular cementation.
Description of the Related Art
A wellbore is formed to access hydrocarbon bearing formations, such as crude oil and/or natural gas, by the use of drilling. Drilling is accomplished by utilizing a drill bit that is mounted on the end of a drill string. To drill within the wellbore to a predetermined depth, the drill string is often rotated by a top drive or rotary table on a surface platform or rig, and/or by a downhole motor mounted towards the lower end of the drill string. After drilling to a predetermined depth, the drill string and drill bit are removed and a casing string is lowered into the wellbore. An annulus is thus formed between the string of casing and the wellbore. The casing string is cemented into the wellbore by circulating cement slurry into the annulus. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain formations behind the casing for the production of hydrocarbons.
Currently, cement flows into the annulus from the bottom of the casing. Due to weak formations or long strings of casing, cementing from the top of the casing may be undesirable or ineffective. When circulating cement into the annulus from the bottom of the casing, problems may be encountered as the cement on the outside of the annulus rises. For example, if a weak earth formation exists, it will not support the cement. As a result, the cement will flow into the formation rather than up the casing annulus.
To alleviate these issues, stage collars have been employed for casing cementing operations. For subterranean vertical wellbores, a free fall cone is used to open the stage collar. However, the free fall cone is unsuitable for deviated and subsea wellbores. For subsea and deviated wellbores, the stage collar has a pressure operated piston for opening thereof. Such a hydraulically operated stage tool is susceptible to premature activation due to pressure spikes in the bore of the casing string which could have catastrophic consequences.